Chapter 1 The Regress Problem Abstract The attempt to justify our beliefs leads to the regress problem. We briefly recount the problem’s history and recall the two traditional solutions, foun- dationalism and coherentism, before turning to infinitism. According to in- finitists, the regress problem is not a genuine difficulty, since infinite chains of reasons are not as troublesome as they may seem. A comparison with causal chains suggests that a proper assessment of infinitistic ideas requires that the concept of justification be made clear. 1.1 Reasons for Reasons: Agrippa’s Trilemma We believe many things: that the earth is a spheroid, that Queen Victoria reigned for more that sixty years, that Stockholm is the capital of Finland, that the Russians were the first to land on the moon. Some of these beliefs are true, others are false. A belief might be true by accident. Suppose I have a phobia which makes me believe that there is a poisonous snake under my bed. After many visits to a psychiatrist and intensive therapy I gradually try to convince myself that this belief stems from traumatic and suppressed childhood experiences. One fine day I finally reach the point where I, nerv- ous and trembling, force myself to get into bed before first looking under it. Unbeknownst to me or the psychiatrist, however, a venomous snake has escaped from the zoo and has ensconced itself under my bed. My belief in the proposition ‘There is a poisonous snake under my bed’ is true, but it is accidentally true. I do not have a good reason for this belief, since I am © The Author(s) 2017 1 D. Atkinson, J. Peijnenburg, Fading Foundations, Synthese Library 383, DOI 10.1007/978-3-319-58295-5_1 2 1 The Regress Problem ignorant of the escape and agree with the psychiatrist that reasons based on my phobia are not good reasons. If however a belief is based on good reasons, we say that it is epistemically justified. Had I been aware of the fact that the snake had escaped and in fact had made its way to my bedroom, I would have been in possession of a good reason, and would have been epistemically justified in believing that the animal was lying under my bed. According to a venerable philosophical tradition, a true and justified belief is a candidate for knowledge. One of the things that is needed in order for me to know that there is a snake under my bed is that the good reason I have for it (namely my belief that the reptile had slipped away and is hiding in my room) is itself justified. Without that condition, my reason might be itself a fabrication of my phobic mind, and thus ultimately fall short of being a good reason. What would count as a good reason for believing that a snake has es- caped and installed itself in my bedroom? Here is one: an anxious neighbour knocks on my door, agitatedly telling me about the escape. But how do I know that what the neighbour says is true? It seems I need a good reason for that as well. My friendly neighbour shows me a text message on his cell- phone, just sent by the police, which contains the alarming news. That seems to be quite a good reason — although, how do I know that the police are well informed? I need a good reason for that as well. I call the head of police, who confirms the news, and says that he was apprised of it by the director of the zoo; I call the director, who tells me that the escape has been reported to her by the curator of the reptile house, and so on. True, my actions are somewhat curious, and they may well signal that a phobia for snakes is not the only mental affliction that plagues me. The point however is not a practical but a principled one. It is that a reason is only a good reason if it is backed up by another good reason, which in turn is backed up by still another other good reason, and so on. We thus arrive at a chain of reasons, where the proposi- tion ‘There is a dangerous snake under my bed’ (the target proposition q)is justified by ‘A neighbour knocks on my door and tells me that a snake has escaped’ (reason A1), which is justified by ‘The police sent my neighbour a text message about the escape’ (reason A2), which is justified by A3, and so on: q ←− A1 ←− A2 ←− A3 ←− A4 ... (1.1) Such a justificatory chain, as we shall call it, gives rise to the regress problem. It places us in a position where we have to choose between two equally unattractive options: either the chain must be continued, for otherwise we 1.1 Reasons for Reasons: Agrippa’s Trilemma 3 cannot be said to know the proposition q, or the chain must come to a stop, but then it seems we are not justified in claiming that we really can know q, since there is no reason for stopping. Laurence Bonjour called considerations relating to the regress problem “perhaps the most crucial in the entire theory of knowledge”, and Robert Audi observes that no epistemologist quite knows how to handle the problem.1 The roots of the regress problem extend far back into epistemological history, and scholars often refer to the Greek philosopher Agrippa. Little is known about Agrippa, apart from the fact that he probably lived in the first century A.D. and might have been among the group of sceptics dis- cussed by Sextus Empiricus, a philosopher and practising physician who al- legedly flourished a century later. Sextus’ most famous work, Outlines of Pyrrhonism, contains an explanation and defence of what he takes to be the philosophy of another shadowy figure, namely Pyrrho of Elis (c. 365–270 B.C.), who himself wrote nothing, but became known for his sober life style and his aversion to academic or theoretical reasoning. So-called Pyrrhonian scepticism advocates the attainment of ataraxia, a state of serene calmness in which one is free from moods or other disturbances. An important technique for reaching this state is the practicing of argument strategies known as tropoi or modes, i.e. means to engender suspension of judgement by undermining any claim that conclusive knowledge or justification has been attained. For example, if it were claimed that a particular sound is known to be soft, a Pyrrhonian would point out that to a dog it is loud, and that we cannot judge the loudness or softness independently of the hearer. Typically, a Pyrrhonian will try to thoroughly acquaint himself with the modes, so that reacting in accordance with them becomes as it were a second nature. In this manner he will be able to routinely refrain from assenting to any weighty proposition q or ¬q, and thus avoid getting caught up in one of those rigid intellectual positions that he loathes so much. In Book 1 of Outlines of Pyrrhonism, Sextus discusses five modes which he attributes to “the more recent Sceptics” (to be distinguished from what he calls “the older Sceptics”), and which Diogenes Laertius in the third cen- tury would identify with “Agrippa and his school”.2 Of these five modes the 1 Bonjour 1985, p.18; Audi 1998, 183–184. The thought is echoed by Michael Hue- mer when he writes that regress arguments “concern some of the most fundamental and important issues in all of human inquiry” (Huemer 2016, 16). 2 Sextus Empiricus, Outlines of Pyrrhonism, Book I, 164; see p. 40 in the transla- tion Outlines of scepticism by Julia Annas and Jonathan Barnes. Diogenes Laertius, Lives of eminent philosophers, Volume 2, Book 9, 88. We thank Tamer Nawar and an anonymous referee for guidance in matters of ancient philosophy. 4 1 The Regress Problem three that are of especial interest are the Mode of Infinite Regress, the Mode of Hypothesis, and the Mode of Circularity or Reciprocation. Here is how Sextus explains them: In the mode deriving from infinite regress, we say that what is brought for- ward as a source of conviction for the matter proposed itself needs another source, which itself needs another, and so on ad infinitum, so that we have no point from which to begin to establish anything, and suspension of judgement follows. ...Wehavethe mode from hypothesis when the Dogmatists, being thrown back ad infinitum, begin from something which they do not establish but claim to assume simply and without proof in virtue of a concession. The reciprocal mode occurs when what ought to be confirmatory of the object under investigation needs to be made convincing by the object under inves- tigation; then, being unable to take either in order to establish the other, we suspend judgement about both.3 In other words, whenever a ‘dogmatist’ (as Sextus calls any philosopher who is not a Pyrrhonian sceptic) claims that he knows a proposition q, the Pyrrho- nian sceptic will ask him what his reason is for q. After the dogmatist has given his answer, for example reason A1, the sceptic will ask further: what is your reason for A1? In the end it will become clear that the dogmatist has only three options open to him, jointly known as ‘Agrippa’s Trilemma’: 1. He goes on giving reasons for reasons for reasons, without end. 2. He stops at a particular reason, claiming that this reason essentially justi- fies all the others that he has given.